They described as ''selective'' the government's decision to prosecute the two former police officers whose disclosures about the assassination of political dissenters by policemen opened the controversy.

Lawyers for Human Rights, which made allegations against several police officials up to the rank of major general, said de Klerk's decision Thursday night to allow police and justice officials to investigate the alleged death squads would not assure clarification of the facts about the assassinations.

''The public has to be assured of an evenhanded approach, and selective prosecutions should be ruled out,'' said Peter Mothle, director of the lawyers' group. He termed the action a ''perversion of justice.''

The South African Council of Churches said it is clear the government intends to cover up police involvement in political murders.

In rejecting demands for a judicial inquiry, de Klerk said several serving and retired police officers will be investigated and five have requested suspension until legal proceedings are complete. Authorities said the five include two police majors, a captain, a sergeant and a constable.

Justice Minister Kobie Coetsee said later that charges - presumably for murder - will be brought against former police officers Butana Nofomela, who is awaiting execution for a non-political murder, and Capt. Dirk Coetsee. After leaving the country, Coetsee said in newspaper interviews that he directed Nofomela and other members of his assassination squad to murder Griffiths Mxenge, a prominent Durban civil rights lawyer, in 1981. The Coetsees are not related.

Nofomela, Capt. Coetsee and another former policemen have said they were ordered by superiors, some of whom still occupy senior positions in the police force, to carry out murders, kidnappings, arson and burglaries against anti-government activists in South Africa and neighboring countries.

A white former narcotics detective sergeant has been arrested in connection with the assassinations earlier this year of two prominent white anti-apartheid activists, David Webster and Anton Lubowski.

De Klerk said he has given a list of alleged victims of assassinations to the justice minister for investigation.